A novel wideband bandpass filter using square loop resonator and thee-coupled line load

A new wideband bandpass filter (BPF) using square loop resonator is presented. The new load is introduced. This load consists of three-coupled lines connected to the high impedance transmission line. With the corresponding length of the coupled lines and the transmission line, the capacitive and inductive properties are obtained. To improve the filter performance, the three-line coupled line load is used and placed at the middle of the transmission line on the upper part of the resonator. In addition, the stubs are connected at the corners of the square loop resonator, leading to the broaden bandwidth. For the better band rejection, the interdigital feed lines are utilized to connect at feed lines. As the experimental results, it is found that this filter gives the bandwidth of approximately 2.27 GHz or the fractional bandwidth of 79.5 percent and the return loss of 20dB. The measured frequency responses of the bandpass filter are well agreed with the responses from the simulation.